The invention relates to a method for determining whether an exhaust temperature sensor of a turbocharged diesel engine is abnormal or not and diagnosing the fault. The method for determining whether the exhaust temperature sensor of the turbocharger diesel engine is abnormal or not comprises the following steps that firstly, the acquired value is compared with the observed value, whether the abnormity happens or not is judged according to whether the acquired value exceeds the observed value error zone or not and the times of generation of the situation that the acquired value changing rate exceeds the observed value maximum changing rate during abnormity; and secondly, whether the sensor fails or not is judged according to the length of time on the situation that the acquired value exceeds the observed value error zone and the times of generation of the situation that the acquired value changing rate exceeds the observed value maximum changing rate within the fixed time quantum during the abnormity. By the adoption of the method, quick diagnosis and accurate positioning can be achieved, and the quick maintenance is achieved.